Trial lecture
December 1st, 10:15 AM, Auditorium 3, Chemistry building
Trial lecture title:
“Materials and interface challenges in solid state batteries”
Kreeringssammendrag/Conferral summary
Faststoffelektrolytter kan i fremtiden gjøre batterier sikrere, siden de erstatter flytende elektrolytter som er kjent for å starte og akselerere batteribranner, i tillegg til å slippe ut giftige gasser. Den største begrensningen for faststoffelektrolytter er ioneledningsevne, som dermed må forbedres om faststoffelektrolytter skal kommersialiseres. Dette doktorgradsarbeidet har undersøkt ioneledningsmekanismen og den lokale strukturen til en mulig faststoffelektrolytt (det lagdelte oksidet Na2Zn2TeO6). Konduktivitet og fasestabilitet i lagdelte materialer er kjent for å påvirkes av Na-innholdet, som vi endrer ved å erstatte rammeverkkationene Zn og Te med Ga og Sb.
Main research findings
Solid-state batteries are currently limited by low ionic conductivity compared to the liquid analogue, and improving ionic conductivity is a major concern for commercialization. This thesis focuses on the local structure and ionic conductivity mechanism of a solid-state electrolyte candidate (the layered oxide Na2Zn2TeO6). The Na content of layered materials is well known to influence conductivity and phase stability, and in this work this is changed by substituting the framework cations Zn and Te with Ga and Sb.
The first work of this thesis establishes a reliable synthesis route for the substituted materials, ensuring and confirming homogeneous distribution of the substituent by nuclear magnetic resonance spectroscopy (NMR). The decreased Na content is found to increase local motion of Na, but this is not translated to long range motion of ionic conductivity. Decreasing the Na-content is therefore not enough to improve ionic conductivity.
This work finally made an in-depth study of complex ordering schemes that may occur in multicomponent layered oxides. The real situation can indeed be very complex, compared to the rather simple average picture description.